Using Drosophila to Study Host-Pathogen Interactions
Model Organisms Studying host-pathogen interactions is extremely important from a medical standpoint because if we can better understand these interactions generally, we can apply the knowledge to many different situations in humans. This is the primary reason for using a model organism to study such interactions. Model organisms are very well understood by researchers in the field which makes them excellent candidates when studying poorly understood phenomena. Specifically ''Drosophila melanogaster, ''has been chosen because it has many aspects in its development and behavior that parallel those in humans. Beckingham, Kathleen M., et al. "[http://gravitationalandspacebiology.org/index.php/journal/article/view/343 Drosophila melanogaster-the model organism of choice for the complex biology of multi-cellular organisms]." ''Gravitational and Space Research'' 18.2 (2007). Genetic Study In 1997 a study was published where the authors were studying ''Drosophila ''in order to gain a better understanding about how immune systems respond when stressed with an invading pathogen. Lemaitre, Bruno, Jean-Marc Reichhart, and Jules A. Hoffmann. "[http://www.pnas.org/content/94/26/14614.short Drosophila host defense: differential induction of antimicrobial peptide genes after infection by various classes of microorganisms]." ''Proceedings of the National Academy of Sciences'' 94.26 (1997): 14614-14619. Interestingly, this study had been done prior to having the completed genome of ''Drosophila ''available for them to study. Apart from the reasons mentioned previously, ''Drosophila'' was an excellent choice for this project mainly due to the environment in which it normally inhabits. ''Drosophila ''spends its entire life cycle in decaying organic matter. Such an environment is filled with microorganisms that are capable of infecting the fly. Therefore it would make sense that ''Drosophila ''has evolved mechanisms capable of dealing with pathogen attacks. For the study, separate populations of ''Drosophila ''were created that had been injected with assortments of either bacterial or fungal pathogens. Sharp needles were dipped in concentrated cultures of the microorganisms and the ''Drosophila ''flies were then pricked with the needle to become infected. The goal of the experiment was to isolate the surviving ''Drosophila ''flies and study how the genes responsible for encoding antimicrobial peptides changed their level of expression. Northern blot plots were created to illustrate RNA expression levels over time of specific genes responsible for dealing with microbial invasions. Comparisons to the injury control group show differences between the expression of genes after infection. Gram-negative bacteria are particularly strong inducers of diptericin, cecropin, attacin, and drosocin. Drosomycin, which is a potent antifungal peptide, is poorly induced by Gram-negative bacteria but responds strongly to a fungal invasion of the fly. One of the most interesting parts of this research was that it showed how the immune system of ''Drosophila was'' not overly simplistic and it had the capability to adapt to different invading pathogens. Similarly, the human immune system adapts and responds to invaders depending on the characteristics of the invader. Importance By infecting the flies and screening for the survivors, the researchers were able to study the response of the organism to microbial and fungal invasions. This study is very important for a number of reasons, but primarily it allows us to see how feedback and response networks react to pathogen attacks. Using this information, we can apply that knowledge to more complicated organisms (e.g. humans) to better understand their immune responses to pathogens. Understanding changes in gene expression could be used in future research to develop gene therapy targets to people with compromised immune responses to help prevent opportunistic infections. References